A scientific way to calm and put a crying baby to sleep
The solution is a magic pair of numbers — five and eight — according to Japanese researchers who conducted experiments on 21 mothers trying to rock their little ones to sleep.
Here’s how it works: Walk your baby for at least five minutes without making any sudden movements. At this point, the study says the little one will be quiet, if not asleep. Then sit and hold the baby for another eight minutes before gently placing them in the cradle.
Putting the sleeping infant to bed without first sitting quietly for a full eight minutes ended in disappointment, according to study co-author Dr. Kumi Kuroda, Team Leader of the Department of Afiliative Social Behavior at the RIKEN Center for Brain Science in Saitama, Japan.
“Although we did not predict it, the key parameter for successful laying down of sleeping infants was the (delay) of falling asleep,” Kuroda said in a statement.
“I raised four children and did these experiments, but even I couldn’t anticipate the key findings of this study until the statistical data came in,” Kuroda added.
“Babies are different and (some) may not all respond to this system,” said Shu, who was not involved with the study.
“The goal should be to make sure the baby has a good night’s sleep with this or other technique, and eventually encourage them to fall asleep on their own, both at the beginning of bedtime and during the night (when they wake up),” Shu said in an email.
Heartbeat data key
According to the study, sitting and holding a crying baby didn’t work — monitors showed the baby’s heart rate rose and the behavior continued. Not surprisingly, putting the crying baby straight into the crib didn’t work either.
Only movement calmed the babies, the study found. Within five minutes, everyone of babies carried by walking mothers had stopped crying, heart rate had slowed and 46% of infants were asleep. Another 18% of babies fell asleep within minutes, according to the study.
However, the five-minute walk only resulted in sleep for crying babies. “Surprisingly, this effect was absent when babies were already quiet,” Kuroda said.
Researchers saw similar results when parents pushed babies in strollers, but the effects weren’t as severe.
Now for the even harder part: laying down sleeping babies without waking them up. A third of the babies in the study woke up immediately after lying down, no matter how gentle it was. But it wasn’t the touch of the bed on a baby’s body that woke them up, the study found. Instead, monitors showed the baby’s heart rate skyrocketing when the child was separated from the mother’s body for the first time.
However, when babies were held for an additional eight minutes, they entered a more stable sleep state — one that didn’t waver when they separated from their mother, the researchers found.
Why does carrying work?
Human babies, like other mammals, respond to what is known as the “transport response,” an innate response that occurs in species with infants who are too immature at birth to walk or fend for themselves.
You see it all the time in nature videos: mother lions, tigers and other wild cats, as well as their domesticated cousins, carry their babies on the scruff of their necks. Likewise wild and domestic dogs, mice and rats. Great apes, monkeys, and other primates carry their babies on their backs, where babies settle and cling, as do possums and giant anteaters. Marsupials like kangaroos, koalas, and wallabies all have special pouches to cuddle their babies as they grow.
Unfortunately, humans don’t seem to be as lucky as other mammalian mothers and have to carry their young longer to get the same response. There is something else that distinguishes people — the need for human babies to learn to sleep on their own.
“Holding or rocking a baby completely to sleep creates a routine that the baby learns to expect,” Shu said. “If the baby wakes up in the middle of the night from a light sleep stage (like all of us), the routine may need to be repeated.”
And don’t rush to soothe a baby over 3 months when he wakes up, the AAP recommends. Just like adults, the baby can also wiggle and fidget and fall asleep again.